Preheat your oven to 350 degrees F. Lightly grease a 9x13-inch baking dish or an oval ceramic baking dish with butter or nonstick spray.

In a large mixing bowl, combine the drained crab meat, cream of mushroom soup, mayonnaise, sour cream, diced onion, diced green bell pepper, lemon juice, Old Bay seasoning, garlic powder, black pepper, and half of the shredded cheddar. Stir until evenly mixed.

Transfer the crab mixture to the prepared baking dish and spread into an even layer.

Sprinkle the remaining shredded cheddar over the top of the casserole.

In a small bowl, toss the panko breadcrumbs with the melted butter until coated. Scatter the buttered breadcrumbs evenly over the cheddar layer.

Bake uncovered for 30 to 35 minutes, until the top is golden brown and the edges are bubbling.

Remove from the oven and let rest for 5 minutes before serving. Serve with a squeeze of fresh lemon if desired.